Bbc tune up help please.

lets see what we can do to help you here. That is kinda a wide open question but maybe we can put you on the right track. Let me ask some questions.....

When you say the altitude is 1500ft or 2500ft are you talking actual altitude above sea level or computing Density Altitude?

How much boost are you making at 8000 rpm in high gear and what is the max boost you are seeing.

What is your fuel pressure at 8000 rpm in high gear and is that measured before or after the barrel valve?

Are you running any high speeds? how many, what jet size and what is the crack pressure of the poppets.

Have you read my Blown Alcohol Plug Reading article at http://www.dragstuff.com/techarticles/reading-alcohol-spark-plugs.html

 

Your EGTs are close. You are getting there, just adjust by 5 sizes on the mainjet at a time.

Since you are still rich you can safely switch the 140 jet into the pump loop and make the mainjet a 92 at what ever density altitude you were last at. Lets say 1500 ft density altitude. In case you are not then adjust the mainjet by 5 for every 500 ft change. So if you change from 1500 ft to 2000 ft then change the mainjet from 92 to 97, or if you go down to 1000 ft then bring the mainjet down to a 87. Now from that start increasing the main jet by 5 at a time a run so if you are at 1500ft then use a 102 and check the EGTs, then a 107 main jet.

It appears that your pump is to big for your motor. You can switch the pump loop to a 150 jet then reduce the mainjet by 10 to try and help. The other trick is to run a 10% underdrive on you pump to reduce the output or add a second pump loop to bypass fuel. You can see the problem because you are running a 115 high speed, a 140 main jet and a 92 pump loop right now. Wow, that is bypassing a lot of fuel.

When you increase the EGTs also keep balancing the port nozzles to the temps tightly clustered. Once you get to 1050* then really start using your plugs to balance the cylinders and make them read all the same. You are going to have to decide how lean you want to go. I would imagine with a new set of plugs they still look pretty new after one run with maybe just coloring on the grandstrap. If you make that flat base turn dark gray in one run then you are still real safe.

At zero ft in DA 29 lbs of boost at 8000 RPM needs around 9.5 -9.8 GPM of fuel (still safe) in the quarter mile.

 

Try 160* to start with

 

Great glad I could help. let me know if you have any other questions. I know several racers down there.